Known in the art is a process for preparing diphenylphosphinylacetic acid hydrazide (DPAH) which comprises interaction of diphenylchlorophosphine with ethanol in the medium of ethyl ether in the presence of triethylamine; separation, by filtration, of the resulting triethylamine hydrochloride; distilling-off the solvent and separation of ethyl ester of diphenylphosphinic acid by distillation. The thus-prepared ethyl ester of diphenylphosphinous acid is converted to ethyl ester of diphenylphophinylacetic acid by reaction with ethyl ester of chloroacetic acid at a temperature within the range of from 100.degree. to 140.degree. C. Then the resulting ethyl ester of diphenylphosphinylacetic acid is dissolved in benzene and recovered from hexane to purify it from the by-products of the reaction. The purified ethyl ester of diphenylphosphinylacetic acid is reacted with hydrazine hydrate at a temperature within the range of from 140.degree. to 150.degree. C., followed by isolation of the desired product and recrystallization thereof from ethanol (cf. Journal of General Chemistry).
The prior art process is a multi-stage process performed under severe temperature conditions and contemplating the use of auxiliary components in certain intermediate reactions as well as hazardous solvents. To ensure the required quality of the desired product in the first stage of the process, it is necessary to purify ethyl ester of diphenylphosphinous acid.
All the above-mentioned features substantially complicate the process and make it difficult to be commercially implemented.